Nitride semiconductor devices play a significant role for high-power and high-frequency applications, due to its outstanding combination of fundamental physical properties, such as large band gaps, large breakdown fields, high electron mobilities, etc. Indium-aluminum-nitride/gallium-nitride (InAlN/GaN) heterostructures are under systematic investigations as an alternative to commercially already available aluminum-gallium-nitride/gallium-nitride (AlGaN/GaN) high-electron-mobility-transistors (HEMTs). The main advantages of the InAiN/GaN heterostructure are the following: 1) an InAlN barrier layer (mole fraction of indium-nitride (InN) of ˜17%) can be grown lattice matched to the GaN thereby mitigate strain related defects and improve their reliability; 2) high spontaneous polarization and thus high charge density in the channel (predicted up to ˜3×1013 cm−2); 3) thin barrier thicknesses of typical InAlN/GaN devices (less than 10 nm) enabling the fabrication of highly scaled devices without the need of gate recesses and 4) high thermal and chemical stability allowing high-temperature large-signal operation at 1000° C. However, traditional AlGaN/GaN HEMTs and InAlN/GaN devices operate in the depletion mode (normally-on), and the depletion mode operation of the InAlN/GaN HEMTs is very inconvenient for power conversion applications in addition to safety concerns.
Further, to achieve the high-power requirement in the specifications, thermal management of HEMT structures is the key determining factor needed to be improved for device power capability.
Accordingly, there is a need for a GaN transistor structure that provides a high electron mobility channel operable in the enhance mode with suppressing heat generation around the channel for high frequency and higher power applications.